Recycled Pulsars Thesis by Bryan Anthony Jacoby In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy California Institute of Technology Pasadena, California 2005 (Defended December 8, 2004) ii c 2005 Bryan Anthony Jacoby All Rights Reserved iii Acknowledgements I would like to thank some of the many people who have influenced and contributed to me and this work. Those who have my gratitude are too many to thank here, but I will do my best. But first, I would like to acknowledge the generous financial support of the NSF Graduate Research Fellowship Program and the NRAO GBT Student Support Program that made this work possible. My mother has always encouraged my curiosity and supported my interest in science, even when it involved sacrifice on her part. I hope that I will be as good a parent. Alex Wolszczan, along with Stuart Anderson and Brian Cadwell, introduced me to the fascinating world of pulsars and radio instrumentation as an undergraduate at Penn State. I am lucky to have had Stuart as a willing mentor for the past decade. I am grateful to my advisor, Shri Kularni, for providing the direction and resources for this research, and for his insights which continue to amaze me. Matthew Bailes has served as unofficial co-advisor and treated me like a member of his group from the beginning; I have learned much from him. I have had the privilege of learning from several other exceptional astronomers. My time with Don Backer has been a true highlight, both personally and educationally. Marten van Kerkwijk, Deepto Chakrabarty, and Dale Frail have been generous and patient as well. The members of the Swinburne pulsar group (past and present), namely Steve Ord, Aidan Hotan, Haydon Knight, Willem van Straten, Russell Edwards, and Craig West, have become not only valued colleagues but also very good friends. Along with the many other people I have had the good fortune of knowing at Swinburne, Parkes, and Green Bank, they have made my long stints away from home much more pleasant as well as productive. I have spent less time observing at Palomar but it is one of my favorite places, largely because of the exceptional people who work there. So many of my fellow grad students at Caltech have helped me in some way over the iv past several years that it is hopeless to try to thank them all. I have shared an interest in neutron stars with David Kaplan, Adam Chandler, and Rick Jenet, and fear that I have learned more from them than I managed to teach in return. Brian Cameron, a recent addition to the team, has been a pleasure to work with; I greatly appreciated his willingness to help with observing and other responsibilities in the stressful late stages of writing this thesis. Edo Berger has kindly helped me several times with data analysis. I also thank Jon Sievers, Pat Udomprasert, Cathy Slesnick, Melissa Enoch, Josh Eisner, George Becker, and Stuartt Corder for being accommodating and enjoyable office mates. My classmates Mike Santos and Matt Hunt are great friends and are two of the most interesting people I know. Mike, along with Rob Simcoe and Micol Christopher, helped to provide an outlet for me through their hard work captaining the Cataclysmic Variables, our department soccer team. Thanks to people here in Robinson would be incomplete without mentioning our crack team of systems administrators, Patrick Shopbell, Cheryl Southard, and Anu Mahabal, without whom very little would get done around here. John Yamasaki’s work on pulsar instrumentation was critical to my research and I have missed him since he left Caltech. This thesis is dedicated to my wonderful wife Megan, whose love and support have sustained me throughout this work. v Abstract We present the results of a large-area survey for millisecond pulsars (MSPs) at moderately high galactic latitudes with the 64 m Parkes radio telescope, along with follow-up timing and optical studies of the newly-discovered pulsars and several others. Major results include the first precise measurement of the mass of a fully recycled pulsar and measurement of orbital period decay in a double neutron star binary system allowing a test of general relativity along with improved measurements of the neutron star masses. In a survey of ∼ 4, 150 square degrees, we discovered 26 previously unknown pulsars, including 7 “recycled” millisecond or binary pulsars. Several of these recycled pulsars are particularly interesting: PSR J1528−3146 is in a circular orbit with a companion of at least 0.94 M⊙; it is a member of the recently recognized class of intermediate mass binary pulsar (IMBP) systems with massive white dwarf companions. We have detected optical counterparts for this and one other IMBP system; taken together with optical detections and non-detections of several similar systems, our results indicate that the characteristic age τc = P/2 P˙ consistently overestimates the time since the end of mass accretion in these recycled systems. This result implies that the pulsar spin period at the end of the accre- tion phase is not dramatically shorter than the observed period as is generally assumed. PSR J1600−3053 is among the best high-precision timing pulsars known and should be very useful as part of an ensemble of pulsars used to detect very low frequency gravitational waves. PSR J1738+0333 has an optical counterpart which, although not yet well-studied, has already allowed a preliminary measurement of the system’s mass ratio. The most signif- icant discovery of this survey is PSR J1909−3744, a 2.95 ms pulsar in an extremely circular 1.5 d orbit with a low-mass white dwarf companion. Though this system is a fairly typical low-mass binary pulsar (LMBP) system, it has several exceptional qualities: an extremely narrow pulse profile and stable rotation have enabled the most precise long-term timing ever reported, and a nearly edge-on orbit gives rise to a strong Shapiro delay signature in vi the pulse timing data which has allowed the most precise measurement of the mass of a millisecond pulsar: mp = (1.438 ± 0.024) M⊙. Our accurate parallax distance measure- +0.08 ment, dπ = (1.14−0.07) kpc, combined with the mass of the optically-detected companion, mc = (0.2038 ± 0.0022) M⊙, will provide an important calibration for white dwarf models relevant to other LMBP companions. We have measured the decay of the binary period of the double neutron star system PSR B2127+11C in the globular cluster M15. This has allowed an improved measurement of the mass of the pulsar, mp = (1.3584 ± 0.0097) M⊙, and companion, mc = (1.3544 ± 0.0097) M⊙, as well as a test of general relativity at the 3% level. We find that the proper motions of this pulsar as well as PSR B2127+11A and PSR B2127+11B are consistent with each other and with one published measurement of the cluster proper motion. We have discovered three binary millisecond pulsars in the globular cluster M62 using the 100-m Green Bank Telescope (GBT). These pulsars are the first objects discovered with the GBT. We briefly describe a wide-bandwidth coherent dedispersion backend used for some of the high precision pulsar timing observations presented here. vii Contents Acknowledgements iii Abstract v 1 Introduction 1 2 A Large-Area Survey for Radio Pulsars at High Galactic Latitudes 5 2.1 Introduction.................................... 6 2.2 ObservationsandAnalysis. ... 7 2.3 DetectedPulsars ................................. 10 2.4 Implications for Sub-Millisecond Pulsars . ......... 26 2.5 Conclusions .................................... 29 3 Discovery of Six Recycled Pulsars in a High Galactic Latitude Survey 31 3.1 Introduction.................................... 32 3.2 AHighLatitudePulsarSurvey . 32 3.3 Discovery and Timing of Six Recycled Pulsars . ....... 33 3.3.1 PSR J1528−3146: Massive Companion . 35 3.3.2 PSR J1600−3053: High Timing Precision LMBP . 35 3.3.3 PSR J1738+0333: Short Binary Period LMBP . 35 3.3.4 PSR J1741+13: LMBP with Strong Scintillation . 39 3.3.5 PSR J1933−6211:LMBPorIMBP? .................. 39 3.3.6 PSR J2010−1323:IsolatedMSP .................... 41 4 PSR J1909−3744: A Binary Millisecond Pulsar with a Very Small Duty Cycle 43 4.1 Introduction.................................... 44 viii 4.2 PulseTiming ................................... 45 4.2.1 ShapiroDelay............................... 49 4.2.2 Distance.................................. 50 4.3 Optical Observations of the White Dwarf Companion . ........ 50 4.4 Conclusions .................................... 52 5 The Mass of a Millisecond Pulsar 55 5.1 Introduction.................................... 56 5.2 ObservationsandPulseTiming . 57 5.2.1 Shapiro Delay and Component Masses . 58 5.2.2 Distance and Kinematic Effects . 58 5.3 Conclusions .................................... 63 6 Optical Detection of Two Intermediate Mass Binary Pulsar Companions 65 6.1 Introduction.................................... 66 6.2 Observations ................................... 67 6.3 DiscussionandConclusions . 70 7 Measurement of Orbital Decay in the Double Neutron Star Binary PSR B2127+11C 73 7.1 Introduction.................................... 74 7.2 ObservationsandAnalysis. 74 7.3 Discussion..................................... 75 7.3.1 Post-Keplerian Observables for M15C . 75 7.3.2 Kinematic Effects on Pulse Timing . 79 7.3.3 Component Masses of M15C and a Test of General Relativity . 80 7.3.4 ProperMotionofM15.......................... 80 7.3.5 Intrinsic Spin Period Derivatives . 83 A Pulsars in M62 85 B A Wide-Bandwidth Coherent Dedispersion Backend for High-Precision Pulsar Timing 87 ix List of Figures 2.1 Surveysensitivity. .............................. ... 9 2.2 Example millisecond pulsar candidate. ........ 11 2.3 Exampleslowpulsarcandidate.. ..... 12 2.4 Pulseprofilesof19newslowpulsars.. ...... 15 2.5 Timingresidualsfor10newslowpulsars. ....... 16 2.6 Timingresidualsfor9newslowpulsars. ....... 17 2.7 Spin period – magnetic field strength diagram. ........ 19 2.8 Spin period distribution of pulsars in survey region. ............ 23 2.9 Dispersion measure distribution of pulsars in survey region..........